Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheromas or plaques, on the walls of blood vessels. While some plaques are relatively stable, others are vulnerable to rupture and release their contents into the bloodstream, causing a blood clot to form. Heart attacks and other acute cardiovascular events usually result from the rupture of high-risk, vulnerable plaques in coronary arteries. Vulnerable plaques are believed to have three major characteristics—a deposit of lipids, a thin cap of fibrous material covering the lipid pool, and infiltration of the immune cells called macrophages. Such deposits occur in both the peripheral blood vessels and the coronary vessels. When deposits accumulate in localized regions of a blood vessel, stenosis, or narrowing of the vascular channel occurs. Blood flow is restricted and the person's health is at serious risk. Early detection and characterization of arterial plaque can identify patients who are unaware that they are at risk of suffering a myocardial infarction or other cardiovascular events such as stroke.
Optical coherence tomography (OCT) has been used to successfully image various organs and tissues. OCT can produce a relatively high resolution image, especially when compared to other imaging modalities. OCT imaging of arterial plaques, however, has had limited success and has been unsatisfactory for identification of vulnerable plaques. Methods and apparatuses for high resolution OCT images are needed for imaging arterial plaques and for identifying vulnerable plaques. Moreover, similar methods and apparatuses are needed for imaging of other normal and diseased tissues, compositions, cells, and pathologies in a subject, including cancer and pre-cancerous conditions.